diff --git a/groovy/Dockerfile b/groovy/Dockerfile
index 065f165..b0db135 100644
--- a/groovy/Dockerfile
+++ b/groovy/Dockerfile
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM java:8
+FROM java:8@sha256:c1ff613e8ba25833d2e1940da0940c3824f03f802c449f3d1815a66b7f8c0e9d
 MAINTAINER Ray Tsang <saturnism@gmail.com>
 
 ENV SRC_DIR /app/src